Deathbed Star Gives Sneak Peek of Our Sun’s Demise

Chi Cygni, a red giant star as shown in this artist's conception, is nearing the end of its life. As it runs out of fuel, it pulses in and out, beating like a giant heart and ejecting shells of material.Credit: ESO/L. Calçada

A preview of what's in store for our sun is in view across
the galaxy, as a similar star balloons in its dying throes.

This sun twin, called Chi Cygni, lies
about 550 light-years away from Earth. As it nears the end of its life, it has
bloated in size and begun to pulse in and out like a giant beating heart. These
are the telltale signs of a star running out of fuel after billions of years
shining bright.

New close-up photos of this star are
offering a sneak peak at our own sun's
demise. The sun is now 4.6 billion years old.

"This work opens a window onto
the fate of our sun five billion years from now, when it will near the end of
its life," said astronomer Sylvestre Lacour of the Observatoire de Paris.

Chi Cygni is now in a phase of its
life called the red giant stage where it has inflated so much that, were it in
our solar system, it would engulf every planet out to Mars. And indeed, the sun
will likely do just that one day when it is a red
giant. At that point, the Earth will most likely be
toast.

A particularly interesting feature
captured by the new data is Chi Cygni's pulsations, which occur once every 408
days. As the star begins to run out of hydrogen fuel for fusion burning in its
core, it cycles through stages of contracting and expanding, causing it to
brighten and dim in the sky. These pulsations allow it to jettison its outer
gaseous layers, which will eventually become a colorful planetary nebula.

At its smallest, Chi Cygni's diameter
is 300 million miles (483 million km). At this stage it is at its hottest, with
giant plumes of hot plasma churning on its surface. When it expands, the star
cools and dims, reaching a maximum diameter of about 480 million miles (772
million km).

The new photos were captured with the
Smithsonian Astrophysical Observatory's Infrared Optical Telescope Array
(IOTA), at Whipple Observatory on Mount Hopkins, Ariz. This network of
interconnected telescopes combines the light from several telescopes into one
image, to yield a resolution equivalent to an observatory as large as the
distance between them.

"IOTA offered unique
capabilities," said researcher Marc Lacasse of the Harvard-Smithsonian
Center for Astrophysics. "It allowed us to see details in the images which
are about 15 times smaller than can be resolved in images from the Hubble Space
Telescope."

The team published their findings in a
recent issue of The Astrophysical Journal.